Colour photography



United States Patent 3,002,?64 COLOUR PHOTOGRAPHY Ernst Keller, Peter Hindermann, and Jean-Pierre Jung,

all of Basel, Switzerland, assignors, by mesne assignments, to Ilford Limited, llford, England, a British company No Drawing. Filed Apr. 14, 1958, Ser. No. 728,065 Claims priority, application Great Britain Apr. 29, 1957 6 laims. (Cl. 260-187) This invention relates to colour photography and particularly to the silver-dye-bleach process of colour photography.

This important method of producing colour records is based on the following general procedure. A photographic silver halide emulsion layer, usually a gelatino silver halide emulsion layer, includes as a uniform dispersion therein, a suitable dyestufi. The layer is exposed to light or otherwise rendered developable so that a latent silver image is formed therein. This image is developed to a silver image. The layer is then treated with a bleach bath which has the efifect of oxidising the silver image and simultaneously reducing (or bleaching) the dyestuff in the region of the silver image. The silver salts and any residual silver are then removed from the layer and the layer then contains only a dyestuli image which is complementary in sign to the original silver image.

Consider-able variations arepossible in this process. For example, the layer may be dyed with the. dyestulf after the exposure step or after the development of the silver image. Moreover, the dyestuif may be included in a plain gelatin layer coated adjacent to the emulsion layer. A large number of patents have been granted in respect of the process, the main details of which can be ascertained from British patent specifications Nos. 397,- 159 and 397,188.

In order to produce a record in full colour there is generally employed a multilayer material which contains three light-sensitive silver halide emulsion layers, one sensitive to blue light only and the others sensitised to greenand red light respectively. To avoid these latter layers from recording blue light in addition to the light to which they are sensitised, it is usual to provide a blue- .absorbing filter layer between these latter layersand the emulsion which is sensitive only to blue, a common form of assembly being:

(a) Support layer (b) Red-sensitive emulsion layer (c) Green-sensitive emulsion layer (d) Blue-absorbing filter layer (e) Blue-sensitive emulsion layer Layer is not always essential since layer (e), when dyed yellow, may provide a suflicient barrier to blue light.

Polychromatic light incident on layer (2) causes the formation of latent silver images in layers (e), (c) and (b), respectively recording in those layers the blue, green and red sensations of the exposing light;

In the silver-dye-bleach process as ordinarily practised, layer (b) is'dyed'blue-green (cyan), layer (c) is dyed magenta and layer (e) is dyed yellow. Accordingly,

when the material is exposed, developed to form silver l images and subjected to the required bleaching treatment and treated to remove residual silver salts and silver, the final product carries positive yellow, magenta and cyan images complementary to' the negative silver images formed on development, so that when viewed it provides an accurate representation of the original subject of the exposure.

One of the principal difliculties in the silver-dye-bleach process is the selection of suitable dyestuffs for the pur- 3,002,964. Patented Oct. 3, 1961 pose. Some hundreds of dyestuifs have been suggested, but most of the dyestuffs proposed are unsatisfactory in one or more respects. A principal difliculty is to ensure that the dyestulf employed will not diffuse from the gelatin emulsion layer in which it is incorporated, and various proposals, such as mordanting, have been made to overcome this difficulty'. In selecting dyestuffs for use, moreover, it is desirable that they should be bleached rapidly by the bleaching baths employed and also preferable that their inclusion in the emulsion layer should not too seriously reduce the sensitivity of the emulsion. In addition, of course, it is desirable that the dye should approach as closely as possible to the theoretical requirement that, of red, blue and green light it should absorb all of one while fully transmitting or reflecting both of the others.

It is a particular difliculty when using disazo dyes that the bleaching tends to occur by breakdown at one of the am groups preferentially, resulting in a variation in hue according to the extent of the bleaching. It is important for their use in colour photography that the hue should be unchanged at dilferent levels of bleaching.

The present invention is concerned with the provision of a new class of cyan dyestuffs for use in the silver-dyebleach process, which approach more closely to the desiderata set forth above.

According to'the present invention a process for the production of a cyan dyestuif image in a photographic layer comprises including in a light-sensitive gelatino silver halide emulsion layer, or in a plain gelatin layer coated adjacent thereto, a cyan dyestuif of the formula:

SOaH

where A is the residue of an aryl carboxylic alkyl ester of which the alkyl group contains at least 5, and preferably at' least 8, carbon atoms, R is a lower alkyl group (i.e. containing up to 6 carbon atoms) or a carboxymethyl group, X is a hydroxyl group or an NHR group where R ishydrogen or an R CO group (where R; is an alkyl, aralkyl or aryl group or halogen-substituted alkyl or aralkyl or aryl group), and n is 1 or 2, forming a latent silver image in said layer, developing said image, subjecting the developed silver image to treatment which bleaches or removes the silver image and simultaneously bleaches the dyestuif in situ therewith, and removing any residual silver and silver salts from the product.

Methods for the production of the foregoing class of dyestufis are exemplified later herein. In general terms they are prepared by diazotising a compound of the formula ANH coupling this With the compound of the formula:

. V SOaH g H diazotising the product and coupling it with a compound of the formula:

.. OH X (SOsH)n the techniques being those generally used in the production of disazo dyestulfs.

v Further according to the invention a process of colour photography comprises a process as just set forth in which the said gelatino-silver-halide layer is sensitive to red light and constitutes one of the layers of a multilayer photographic material which further contains photographic emulsion layers sensitive to blue and green light respectively dyed with yellow and magneta dyestuifs, and the said cyan dyestuff is included in the said red- .sensitivc layer or in a plain gelatin layer coated ad- --jacent thereto. More particularly the invention provides a process in which the said cyan-dyed layer is .layer (b) of an assembly consisting of:

(a) Support layer,

(b) Red-sensitive emulsion layer dyed cyan,

(c) Green-sensitive emulsion layer dyed magneta,

(d) Blue-absorbing filter layer,

(e) Blue-sensitive emulsion layer dyed yellow, optionally with plain colloid separating layers between "some or all of the adjacent layers recited.

The invention further includes such light-sensitive materials employed in the aforesaid processes, and suitable for variants of those processes, which consist of or include a gelatino silver halide emulsion layer containing a cyan dyestuffs as above set forth.

Preferred dyestufis within the general formula given .above are those in which R is a methyl or ethyl group and the sulphonic acid of the middle naphthalene ring is in the 6 or 7 (preferably the 6) position. One of the sulphonic acid groups in the right-hand naphthalene nucleus is preferably in the 4, or 6 position of that nucleus with respect to the 8-hydroxyl group and where a second sulphonic acid group is present it is preferably in the 2, 3 or 4 position depending on the position of the first sulphonic acid group. Preferred positions where two sulphonic acid groups are present are the 3:6 and 2:4 positions.

Specific dyestufis which have been found to be of particular value are set forth in the examples which follow.

The bleaching of the cyan dyestuffs employed in this invention can be effected by any of the types of bleaching bath commonly employed in the silver-dye-bleach process.

The plain use of acid, e.g. hydrobromic or hydrochloric, is eifective but is very slow. The inclusion of halide salts has an accelerating effect, but these bleaching baths are still slow. The inclusion of a solvent for silver halide such as thiourea or pyridine has a strongly accelerative effect, and this can be greatly increased by the inclusion of an accelerating substance or catalyst. In these connections reference may be made to British patent specifications Nos. 397,159 and 490,451 for suitable bleaching baths.

The following example, which for simplicity is concerned only with the treatment of a single layer containing the cyan dyestufi, will serve to illustrate the inven tion.

EXAMPLE Preparation of the dyestufis DYESTUFF N0. 1

CO CmHnn OCHI HO NH-COCH! N=N -N=N SOaH 03H 36.9 parts of 3-amino-4-phenoxybenzene-l-carboxylic ,4 acid n-decyl ester are dissolved at room temperature in 300 parts of alcohol. 40 parts of concentrated hydrochloric acid are added to the mixture and it is then cooled, whereupon the. chlorohydrate precipitates. 40 parts of ice are added and it is diazotised at 0-5 with a concentrated aqueous solution of 6.9 parts of sodium nitrite. After stirring for 2 hours at 0-5 and decomposing a little excess nitrous acid, the pale yellowish coloured, clear diazo solution is poured within 2 hours into a suspension of 25.3 parts of l-arnino-Z-methoxynaphthalene-6-sulphonic acid and 60 parts of sodium acetate in 500 parts of water and 500 parts of ice. This is performed at 0-5 The coupling occurs immediately and the colour changes to red. The whole is stirred for 6 hours at this temperature, the acid is then neutralised by the gradual addition of 32 parts of sodium carbonate and the precipitated dyestutf is filtered off under suction. it is washed in the suction filter with a 5% sodium chloride solution.

The brownish-red monoazo dyestutf is dissolved at the boil in 4000 parts of hot water in the presence of 2 g. per litre of the condensation product of dodecyl alcohol and 20 mol of ethylene oxide as dispersing agent, 6.9 parts of sodium nitrite are added, the reaction mixture is cooled to 25 and 40 parts of concentrated hydrochloric acid are added. After stirring for 15 hours at 2530 a little excess nitrous acid is decomposed with sulphamic acid. The brown-yellowish gelatinous diazo emulsion is then poured at 1520 into a solution of 36.1 parts of 1-acetylamino-8-hydroxynaphthalene- 3.6-disulphonic acid and parts of sodium acetate in 1000 parts of water and 250 parts of pyridine. The coupling takes place immediately and the colour changes to cyan. Stirring is continued for 4 hours at the same temperature, 600 parts of potassium chloride are added and the dyestuif which precipitates is filtered oti under suction. It is washed first with 500 parts of a solution consisting of 50 parts of pyridine, 25 parts of potassium chloride and 350 parts of water, then with 500 parts of pyridine and, finally, with 200 parts of acetone, after which it is dried at 80.

The dyestuif is a blue powder which dissolves in water with a cyan colouration and in concentrated sulphuric acid with a blue colouration.

The 3-amino-4-phenoxybenzene-l-carboxylic acid decyl ester used as starting component is obtained by condensing 4-chloro-3-nitrobenzene-1-carboxylic acid with excess phenol in the presence of 2.2 mol of potassium hydroxide at temperatures of over C., isolating the free 4- phenoxy-3-nitrobenzene-1-carboxylic acid, converting this with thionyl chloride into carboxylic acid chloride, reacting the chloride with n-decyl alcohol to form the decyl ester and finally reducing the nitro group to the amino group in aqueous ethyl alcohol.

The following table contains some further disazo dyestufis which can be used and which can be produced by the method described above. If the starting components are homologous and isomeric or analogous compounds, they are also contained by the method described above.

DYESTUFF NO. 2

C O O OioHun 0 CH; IEIO 11TH:

N=N' -N=N SOsH SO 3H SOaH 36.9 parts of 3-amino-4-phenoxy 1-carboxylic acid-ndecyl ester are diazotised as described in the example of Dyestutf No. l and coupled with 25.3 parts of l-amino-2- swam methoxynaphthalene 6-sulplionic acid. This brown-re monoazo dyestufi is'jdissolvedfin 4000 parts of boiling water in the presence of 2 g. per litre of the condensation product from 1 mol of dodecyl alcohol and 20 mol of ethylene oxide as dispersing agent, 6.9 parts of sodium nitrite are added, the temperature is reduced to 25 C. and 40 parts of concentrated hydrochloric acid are added. After stirring for 15 hours at 2025 C. and decomposition of a little excess nitrous acid, the brown-yellow' diazo suspension is poured at 20-25" into a solution of 31.9 parts of 1-amino-8-hydroxynaphthalene-3.6-disulphonic acid and 80 parts .of. sodium acetate in IOOO-parts of water and 250 parts of pyridine. Coupling occurs immediately and the colour changes to cyan. After stirring for 6 hoursat 10-15 C., 600 parts of potassium chloride are added, the dyestuif suspension is heated to 40 C. The precipitated blue disazo dyestuif is filtered off under suction and washed first with a solution consisting of 50 parts of pyridine, 25 parts of potassium chloride and 350 parts of water, then with 500 parts of pyridine and finally with 200 parts of acetone, after which the dyestuif is dried in the vacuum at 7080 C.

The dyestuif is a blue powder which dissolves in water with a cyan colouration and in concentrated sulphuric acid with a deep .blue colouration.

DYESTUFF NO. 3

s|08H 27.7 parts of 4-arninobenzene-l-carboxylic acid-n-decyl ester are suspended in 200 parts of water and 30. parts of hydrochloric acid and 'diaz'otised at *2" C. with 6.9" parts of sodium nitrite.j The clear solution of the diazo compound is then poured at 0-5 C. gradually into a suspension of 25.3 parts'of'1-amino-2-methoxynaphthalene-6-su1phonic acid and 60 parts of sodium acetate in 500 parts of Water and 500 parts of ice. The coupling occurs immediately and the colour changes to red. The whole is stirred for 6 hours at-05"- C., the acid is neutralised by the addition of 32 parts of sodium carbonate, the red dyestufi which precipitates is filtered off under suction and washed in thesuction' filter with a sodium chloride solution.

The brown-red. monoazo dyestufi is dissolved in 3000 parts of boiling water, 6.9 parts of sodium nitrite are added, the solution is cooled to 25 C. and 40 parts of SO H- SOsH concentrated hydrochloric acid are added. After stirring 5 for 20 hours at 20-25 C.',' 'a little excess nitrous acid is decomposed with sulphamic acid, the diazo compound is precipitated by the addition of 750 parts of sodium chloride, filtered oil and washed with saturatedsalt solution. The diazo compound is pasted in 1000 parts of 6 ice water and the suspension is added in portions at 15-20 C. to a solution of' 51.9 ansor reminds-11y droxynaphthalene-3.6-disulphonic acid and 40 parts of sodium acetate in 1000 parts of water and 250 parts of pyridine. Coupling occurs immediately and the colour changes to cyan. After stirring for 4 hours at 1520 C. 400 parts of potassium chlorideare added to the dyestuff solution, it is heated to 40 C., the precipitated blue dyestuff is filtered oil under suction and Washed first with 300 parts of a 20% sodium chloride solution, then with 300 parts of pyridine and finally with 200 parts of acetone. It is then dried in the vacuum at 80 C. The dyestuii is a blue powder which dissolves in water with a cyan colouration and in concentrated sulphuric acid with ablue colouration.

DYESTUFF NO. 4

OCH; 110 NH:

SOzH

34.1 parts of- 3-amino-6-phenoxybenzene-l-carboxylic V acid-n-octyl ester are diazotised as described in the example of Dyestuif No. 1 and coupled with 1-amino-2- methoxynaphthalene-6-sulphonic acid. The brown-red monoazo dyestuft is dissolved in 4000,.parts of boiling Water, 6.9 parts of sodium nitrite are added, the temperature is reduced to 25 C. and parts of concentrated hydrochloric acid are added. After stirring for 20 hours and'decomposing some excess nitrous acid, the precipitated diazo compound is filtered oil under suction and Washed with a 20% sodium chloride solution. The

- diazo compound is then-pasted in 1000parts of ice water for use according-to the invention;

and this suspension is added at 20 25 C.in portions to a solution of 31.9 parts of -l-amino-S-hydroxynaphthalane-3,6-disulphonic acid and 40 parts of sodium acetate in 1000 parts of Water and 250 parts of pyridine. vThe coupling occurs immediately and the colour changes to cyan. After stirring for 6 hours at 20-25 C., 180 parts of potassium chloride are added to the dyestuff solution, it is heated to 35 C. and the precipitated blue disazo dyestuffi is filtered off under suction. It is Washedas described in the example of Dyestufi No. l and dried at -80 in the vacuum.

The dyestufi is a blue powder which dissolves in water with a'cyan colouration and'in concentrated sulphuric acid with a dark blue colouration.

The following table lists additional examples of dyes They conform to the formula:

OR OH X .i Nr N- I SOaH Position D A. R X 915035 0 group 5 N%. I lnend 00111130- I nent 5-4.-. 'Gd-Q-coomum 0H3 0H 3:6

a... C -o -oooowm1. 03,. NHL. 24

v (n) v r r Position M8051 Dye A R X group(s) No. 7 end component C -o-C -o00cwm1-. CH3-.. N 4

C -0 -CO0 (m u 0113.. NHGOGQHB as O-o 0000mm! CH3 N11, 4:6

10.--- -0- O (m i1 CH3 NHCOCE- -OL-.. as

CH: 11.... O-o-O-woonn 0H3 NHo0-c. -o1-..- 316 D I CH3 12--.. (m; z1 CH3 NHoooH20- -o1..

13.... oo (s fl C Ha NH: 3:6

14.... 0-C 0C(12 n CH3 NH: 3:6

1s.-. GOG-m- CH3" NE. 3:6

16.... otnu-OwOwoootmtnu- 0H8 NH: 3:5

(terh) 11---- one 00-000mm"--. cm NH, as

(tart) (n) 12.... 0000010311.- 011-5.. NHi... am

I 19.--. QC00C10H21-. CH3. NH: 3:6 20.... G10O- 00 (s 11-- 033.. NH: 3:6

21- G100 O (mh CH3.- NH: 3:6

22.... -o-C -oooo m 1n.- cm- NHi. 3:6

2a.--- GOG-0000 0 -cmcooH-- NH: s=s

2.33 gm. of Dyestufi No. 1 above and 7.4 gins. of dodecyl sodium sulphate are dissolved in 460 cos. of

water. This dye solution is then added to 740 cos. of a silver chlorobromide emulsion containing 2.6 grns. of The mixture is then coated on film base to give a coating weight of 2.7 mgms. of silver silver as silver halide.

per square decimeter.

The dried coating is exposed to light to record an image therein and processed at 68 F. as follows:

(1) Develop to a silver image by two ment in the following developer.

minutes treat- 75 Water to 1 litre.

9 (2) Rinse 30 seconds. (3) Fix in 20% sodium thiosulphate for 3 minutes. (4) Rinse 30 seconds. (5) Harden in 4% formalin. (6) Wash minutes. @(7) Dye bleach for 8 minutes in the following bath:

Water to 1 litre.

(10) Wash 5 minutes.

(11) Fix in sodium thiosulphate for 3 minutes.

12) Wash for 10 minutes and dry.

A reverse image in dye is obtained.

Steps 4 and 5 may be omitted if the original emulsion is hardened or provided with a hardened gelatin supercoat.

Similar results are obtained using the other dyestufis falling within the formula stated, and particularly when using Dyestuffs Nos. 2, 3 and 4 above. When the process is repeated With a similar, but undyed, silver halide emulsion, supercoated on the dyed emulsion, it is found by microscopic examination that substantially none of the dyestulf in the dyed layer migrates to the undyed layer either on coating the film or on processing.

All the said dyestuffs are of satisfactory hue, have very good resistance to migration, bleach rapidly and effectively, and are generally of exceptional value in the silverdye-bleach process of colour photography.

What we claim is:

1. A cyan dyestuif of the formula:

SOsH

S OaH NHn SOBH

3. The dyestuff of the formula:

0 CH3 HO NH:

I SOaH 4. The dyestuir of the formula:

5. The dyestuff of the formula:

C O 0 CaHun 6. The dyestuff of the formula:

C O O CsHnn SOsH SOaH- -SOaH References Cited in the file of this patent UNITED STATES PATENTS 

1. A CYAN DYESTUFF OF THE FORMULA: 